The present disclosure relates to the shape of a connecting portion between wires provided in different wiring layers in a semiconductor integrated circuit.
In a semiconductor integrated circuit, a contact electrically connecting together wires provided in different wiring layers is likely to undergo wire breaking, etc., due to the step between wires or the contact resistance. Therefore, a plurality of contacts are arranged to reduce the resistance, thereby avoiding the occurrence of wire breaking, etc.
FIG. 15 is a plan view showing a connecting portion between wires provided in different wiring layers in a conventional semiconductor device. The conventional semiconductor device includes a semiconductor substrate, a first insulating layer provided on the semiconductor substrate, a wire 103 provided on the first insulating layer, a second insulating layer provided on the wire 103, a bonding pad 101 provided on the second insulating layer, and a wire 102 formed integral therewith. Portions of the wire 102 that are provided in the openings of the second insulating layer each serve as a contact 104 connected to the wire 103. The bonding pad and the wire 102 are formed by aluminum (Al), and the wire 103 is formed by polysilicon. Each contact 104 has a square planar shape.
In the conventional semiconductor device, the connection area of the wire 103, which is used for the electric connection with the wire 102 via the contacts 104, has such a shape that the end portion thereof has an increased width (d2) about several times to some tens of times the wire width (d1) of the other portion and is tapered toward the direction in which the wire 103 extends so that the width gradually becomes equal to the wire width (d1) of the other portion.
Where two wires 102 and 103 are connected with each other via a plurality of contacts 104, the current is concentrated at one or more of the contacts 104 that are located toward the direction in which the wire of the greater wire resistance (the wire 103 in the illustrated example) extends (the rightward direction in FIG. 15; the leading direction of the wire 103). Particularly, the current is concentrated at an end portion of the contact area between the wire 103 and the contact 104 toward the direction in which the wire 103 extends.
For this problem, the conventional semiconductor device includes the wire 103 whose connection area is gradually flared in the hope that the current flows around also to the contacts 104 other than those located toward the direction in which the wire 103 extends.